gomog said:
That was an interesting leap into the unknow! ;)

Actually, over the last few years, I have lost confidence in new parts. So many of them fail from the box. I prefer, wherever possible, to have mine rebuilt or remachined by myself or locally.

If you wish to feel that my use of new spark plugs indicates some failing in my diagnostic ability. So be it.

If you wish to re-use head and crank bolts over and over again as I said before, do so. It is important for the community to have a least a few people who take such risks.

Trevor2 said:
The motor factors rub their hands when you walk in the door. As regards my P38 it's 10 yrs old & is in very "mint" condition with plenty of tlc, not fnb.

That is a new engine in my book, made (I believe) after the LR stretch bolt era began. My blocks are 1963 (Jetfire), 1984 (3.5), 1990 (3.5) 2000 (4.8) and a 4.6 (2004). All running well.

Do you have only the one engine? I imagine that you haven't had to do any major work on it yet. I imagine you will reuse its head and crank bolts when the time comes. Wish I could be there to hand your torque wrench.:D
Click to expand...

You two gona stop it.:eek:
Click to expand...
 
Yes! I am almost sorry I have “only” the “one” engine (& it’s not a “jetfire”) & that’s in the P38DT & that’s where it will stay. What’s all this crap using bolts over & over again? Can’t “you” do the job right the first time? I ask you again? What!!! “qualifications” (& I don’t mean personal experience) do you have to make such/or any statements? With proper examination of a part, there is “no risk” the risk only comes when as you do, don’t know what to replace so you replace whatever! & even then you might not replace the key faulty part, because you “don’t” have the diagnostic skills.

This engine “will” last the life of the vehicle, why? because it gets “regular” sensible maintenance, it doesn’t get stressed, it gets nurtured, it also gets only the parts that is/are required to resolve a fault, it “doesn’t” get “Fit New Brigade” why change one when you can change all attitude. You obviously have little or no background knowledge of mechanics, or you would not produce such “fit new brigade” statements as you do.

The “art” of keeping a vehicle in a legal state as required by law, is to do so by, regular maintenance, diagnostics, sensible repairs at minimum costs. Have you ever maintained a large fleet of vehicles? That, have to make a profit? With your “fit new” attitude, you would probably last till lunch time, you would then get a “new” brush to sweep the garage floor.

To fit a new part, is the last resort, I was trained to diagnose, remove, examine, repair cost effectually, or replace. I say this again, the dealers, motor factors etc. just love the “fit new brigade” & they can spot “you” coming in! why sell you “one”? When they can sell you “four” or “six”, or “eight etc. they F******G love blokes like you, it pays for their holidays!

You’re the sort who changes the expensive lock when only the hinge needs a drop of oil!

Regards Trevor2
 
Trevor, sorry to dig this up, I've been away from the forum for a while but I'll explain what I was on about. Firstly I'm not talking about just head bolts but the theory of fastener engineering.

Trevor2 said:
Doobs,

With regards to “friction” that is why the threads on a nut or a bolt & the block are cleaned & lubricated to reduce the friction as much as reasonably possible.

With regards clamping force & torque, please explain your version further?

When you apply torque to a bolt/nut (torque being “ any force that causes rotation) & clamp, being two objects being secured together. Therefore to join/secure two surfaces together you would apply a specific torque to a nut/bolt to secure the said two surfaces together.

Iff you only use the angle method, how do you know at what final torque you have attained? Being that a specific bolt/nut size will only take a certain amount of stress & I have seen the results/damage by only using the angle method. Aluminium heads & blocks are delicate & require a constant & specific torque.
Click to expand...

When tightening a nut or bolt the goal is to achieve a certain clamp force, that is the force the nut / bolt system applies to the two objects to keep them together. Measuring the torque applied to the fastener is one way of estimating the clamp force achieved, but it is subject to lots of variation, some due to friction variations. This variation can be minimised with proper cleaning / lubrication of the threads. The danger is that while you might achieve a constant clamp load between fasteners you might get the wrong level clamp force in the joint if it was not designed to have lubrication.

We had an issue in plant once where wheel studs suddenly started snapping. We checked and double checked the torque settings on the machine and could find no problem, everything within spec but every vehicle down the line was getting its stud snapped. It turns out the supplier of the studs changed the surface finish of the stud (not added lubrication, just changed the type of coating) which reduced its friction and increased the clamp load beyond what the stud could take. This is an example of clamp load being sensitive to friction levels, too high friction and too low.

Trevor2 said:
Have you ever seriously worked on an engine? ever, attained professional qualifications in motor vehicle mechanics? worked with qualified motor vehicle technicians & also debated the above with the newbies & the oldies? not ever resistant to change however a balance must be made between common sense & practical application from the rule book, blindly follow or interpretation?
Click to expand...

I'm a qualified engineer designing chassis systems for vehicles to be released in 2 to 3 years time. I've done all of the above and debate the torque angle vs torque issue with my colleagues extensively. I must admit I was suspicious but once I looked at a few stress strain curves of bolts and learned how to spec the joint I became convinced that torque angle is the way ahead for the mass production of motor vehicles. It's much more robust then torque only in the manufacturing environment, and as someone responsible for specifying torques for service I'll specify torque and angle if it's used in production (we don't use it on all joints as the tooling is expensive, only on critical ones).

Trevor2 said:
You say “I believe that bolts tightened in this way can be used 4-5 times (loads of disclaimers here” Ideally heads should never have to be removed, once yes/maybe, but 4-5 times something is seriously wrong with the person doing the repairs.
Click to expand...

Agreed, I'm talking about the principle of designing joints, not just head bolts. Brake calliper bolts could be removed 4-5 times during a vehicles life.

Having said all of the above, if what you do works for you then keep at it. Risk judgement is a personal thing. Two people faced with the same set of risks will take different paths.

Andy,

Glad you got to the bottom of your issue.
 
Andy, I am more cynical, the supplier you are talking about, I, suspect was using a cheaper/inferior stud (as always to cut costs), as for friction, it will always be there, a little more or a little less.

Regards Trevor2

As my Father died, two weeks later his Great Grandson was born, evolution never stops, as I go to my grave with my torque wrench (I do have an angle gauge) my son will say to his son, the angle gauge is the only way, his son will say, get real dad, angle gauges went out years ago?
 
Trevor2 said:
Andy, I am more cynical, the supplier you are talking about, I, suspect was using a cheaper/inferior stud (as always to cut costs), as for friction, it will always be there, a little more or a little less.
Click to expand...

You are not cynical Trevor. You simply don't understand the principles involved, whether "neck down", clamp force or the use of plastic deformation for manufacturer benefit (last decade and more). Without that, it is impossible to appreciate the risks involved.

Try the link below, maybe it will help you understand where we have been unable to. There are scores of other articles if you need them as well.

Saturn Head Bolts- Relay2 Relay3 Sky Vue Ion- ARP Unisan
 
Andy, you said previously “risk judgement is a personal thing” it may be in your view, however I have Professional Qualifications in Risk Management, The Institute of Motor Industry, Institute of Road Transport Engineers, Motor Vehicle Technical Engineering etc et. I could go on, I took my last qualification when I was 50! (IOSH) but I hate to bull****.
I have been to University & examined metal stresses etc. as part of my degree in engineering, I have had the similar “implant up my arse” as you have, however I did retain some common sense. It also demonstrated on stretch monitors to destruction new bolts & old bolts in good condition/poor condition, stretch & non stretch bolts ditto. A used bolt in “good” condition made the grade every time.

Saturn Bolts say :- “A Saturn head bolt under load will stretch & spring back to it’s original length when released. However, if it is stretched to far will either become permanently elongated or break.” Any bolt that is streched to far, even new, will fail! Where does it say the bolt “must be changed”? As I have said repeatedly a bolt in good condition & properly examined can be used again.

Saturn Bolts also say :- “It’s extremely important that all Saturn Head Bolts be in perfect condition & are installed & lubricated properly so they are not overloaded.” This goes for any bolt, it's just a blatant disclaimer, when replacing the “used head bolt, you are, I hope not going to overload it (wake up, it’s only nipped up to 65lbsft. 70lblsft. Max. RRV8)

Saturn Bolts also say :- “Recycled head bolts “may” not hold the proper torque & “may” eventually fail if retightened, head bolts that are “too stretched” “may” break or deform & cause head gasket failure.

You could also get a brand new bolt that “may” “fail”! I say again a properly examined & tightened correctly, the bolt will not fail. Saturn only says “may” fail, again a disclaimer.

This whole thing is getting more than a little tedious.

I will quantify my outlook on replacing bolts of any kind & I am persisting in this thread only for the novice DIY people out there who are lead by the “Fit New Brigade” people as yourself & the greedy manufacturers & garages, who advise (only ever advise or say “may”) & will never say “Must” replace this or that in what ever quantity the deem.

May I quote three scenarios, “you” bring your car to me for repair, I can tell by the way you explain the fault, your body language, you may drop into the conversation your mechanical knowledge, the age & condition of your car, your dissatisfaction with motor dealers & repairers in general. From this I will ascertain what level of repair I am going to do, I will “always” repair a vehicle properly & correctly, the difference in your case is “All the Parts Will be Replaced With New” & any other parts I can think of that may be remotely related, no matter what cost, your paying & you love “paying” it gives you reassurance, that the job must have been done correctly & you can brag about it in the pub/bar.

Scenario two, a chap comes to me with the same job as yours, his car is old, a little tatty, by the way he dresses he looks a little hard up, a proud chap, always worked hard. I will repair this car to the highest standard, however fit as little new parts I can get away with, would even get parts from the breakers, he will also brag about it in the bar/pub.

Scenario three, my friend comes to me with the same job as yours & says he needs to have it running so he can part ex against another car. As I have a dislike for car dealers. This job again will be carried out to the highest standard however little or no parts will be replaced, as the vehicle will end up at auction & bring a very low price, the buyer will ascertain what he is getting for his money so I am ok with this.

When replacing any part, safety comes first. Not everyone can go out & buy everything new the job requires, it this was the case there would be no breaker yards, you may be lucky & do this, again, not everyone can.

Trevor2

PS I do actually follow some specs. on modern vehicles, anything after a P38, before that “designers didn’t have the computer models to “neck down” materials & costs to the absolute minimum & profits high like they do now.

Cynical, with common sense, experience & with an eye on costs.








 
I read this thread with interest. It seems to me there is nothing more than a difference of opinion.

Two guys, both highly qualified and experienced but with different views, would it be rude to suggest you need to agree to disagree on certain points and let those of us who are not so expert gain our own understanding of what is good to go and what isn't.

I am no master mechanical engineer but I would have to admit I have re-used head bolts and a variety of others with no problems. I have also come unstuck - I hate having to drill out snapped bolts etc. If a bolt is going to go (and you're lucky) you feel it as it gets upto and beyond its elastic limit but before it reaches failure.

I suppose what I'm saying is that if you are in a make do and mend position, do it but be careful, if you have the money then replace. Either way though, if you don't take proper care in your approach you're gonna break it or get hurt. Nuf said.
 
Trevor2 said:
Andy, you said previously “risk judgement is a personal thing” it may be in your view, however I have Professional Qualifications in Risk Management, The Institute of Motor Industry, Institute of Road Transport Engineers, Motor Vehicle Technical Engineering etc et. I could go on, I took my last qualification when I was 50! (IOSH) but I hate to bull****.
I have been to University & examined metal stresses etc. as part of my degree in engineering, I have had the similar “implant up my arse” as you have, however I did retain some common sense. It also demonstrated on stretch monitors to destruction new bolts & old bolts in good condition/poor condition, stretch & non stretch bolts ditto. A used bolt in “good” condition made the grade every time.

Saturn Bolts say :- “A Saturn head bolt under load will stretch & spring back to it’s original length when released. However, if it is stretched to far will either become permanently elongated or break.” Any bolt that is streched to far, even new, will fail! Where does it say the bolt “must be changed”? As I have said repeatedly a bolt in good condition & properly examined can be used again.

Saturn Bolts also say :- “It’s extremely important that all Saturn Head Bolts be in perfect condition & are installed & lubricated properly so they are not overloaded.” This goes for any bolt, it's just a blatant disclaimer, when replacing the “used head bolt, you are, I hope not going to overload it (wake up, it’s only nipped up to 65lbsft. 70lblsft. Max. RRV8)

Saturn Bolts also say :- “Recycled head bolts “may” not hold the proper torque & “may” eventually fail if retightened, head bolts that are “too stretched” “may” break or deform & cause head gasket failure.

You could also get a brand new bolt that “may” “fail”! I say again a properly examined & tightened correctly, the bolt will not fail. Saturn only says “may” fail, again a disclaimer.

This whole thing is getting more than a little tedious.

I will quantify my outlook on replacing bolts of any kind & I am persisting in this thread only for the novice DIY people out there who are lead by the “Fit New Brigade” people as yourself & the greedy manufacturers & garages, who advise (only ever advise or say “may”) & will never say “Must” replace this or that in what ever quantity the deem.

May I quote three scenarios, “you” bring your car to me for repair, I can tell by the way you explain the fault, your body language, you may drop into the conversation your mechanical knowledge, the age & condition of your car, your dissatisfaction with motor dealers & repairers in general. From this I will ascertain what level of repair I am going to do, I will “always” repair a vehicle properly & correctly, the difference in your case is “All the Parts Will be Replaced With New” & any other parts I can think of that may be remotely related, no matter what cost, your paying & you love “paying” it gives you reassurance, that the job must have been done correctly & you can brag about it in the pub/bar.

Scenario two, a chap comes to me with the same job as yours, his car is old, a little tatty, by the way he dresses he looks a little hard up, a proud chap, always worked hard. I will repair this car to the highest standard, however fit as little new parts I can get away with, would even get parts from the breakers, he will also brag about it in the bar/pub.

Scenario three, my friend comes to me with the same job as yours & says he needs to have it running so he can part ex against another car. As I have a dislike for car dealers. This job again will be carried out to the highest standard however little or no parts will be replaced, as the vehicle will end up at auction & bring a very low price, the buyer will ascertain what he is getting for his money so I am ok with this.

When replacing any part, safety comes first. Not everyone can go out & buy everything new the job requires, it this was the case there would be no breaker yards, you may be lucky & do this, again, not everyone can.

Trevor2

PS I do actually follow some specs. on modern vehicles, anything after a P38, before that “designers didn’t have the computer models to “neck down” materials & costs to the absolute minimum & profits high like they do now.

Cynical, with common sense, experience & with an eye on costs.
Click to expand...

I do risk management aswell, so why do I keep fokin me fingers, me shins and me toes, bent me steering on a tree stump, nocked me light off on a fence, burst a tyre on another fence, and get stuck regularilly when I assessed it as ok.
 
Guys, don't you think that this discussion isn't worth a set of bolts per 50p each? In Poland people aren't very rich, but NOBODY here use headbolts twice.

P.S. what is your opinion about using alloy headgaskets 603796 instead of composite ERR7217?
 
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